In Mexican linguistics, saltillo (Spanish, meaning "little skip") refers to a glottal stop consonant, [ʔ]. It was given that name by the early grammarians of Classical Nahuatl. In a number of other Nahuatl languages, the sound cognate to Classical Nahuatl's glottal stop is [h], and the term saltillo is applied to either pronunciation. The saltillo is often spelled with an apostrophe, though it is sometimes spelled (with either pronunciation) ⟨h⟩, or, when pronounced [h], ⟨j⟩. The spelling of the glottal stop with an apostrophe-like character most likely originates from transliterations of the Arabic hamza. It has also been spelled with a grave accent over the preceding vowel in some Nahuatl works, following Carochi 1645.

The saltillo represents a phoneme in many American languages besides Nahuatl, which means that its presence or absence can change the meaning of a word. However, there is no saltillo in standard Spanish, so the sound is often imperceptible to Spanish speakers, and Spanish writers usually did not write it when transcribing Mexican languages. This meant that, for example, Nahuatl /ˈtɬeko/ "in a fire" and [ˈtɬeʔko] "he ascends" were both written tleco.

The saltillo symbol is also being used in at least one Southeast Asian language, Central Sinama of the Philippines and Malaysia. It represents both the glottal stop and the centralized vowel [ə].

This letter corresponds to two code points in Unicode, starting in Unicode 5.1: U+A78BꞋlatin capital letter saltillo (HTML &#42891;) and U+A78Cꞌlatin small letter saltillo (HTML &#42892;). These are normally rendered as a straight apostrophe-like symbol, sometimes described as a dotless exclamation point. In earlier versions of Unicode, saltillo was provisionally represented by such characters as U+02BCʼmodifier letter apostrophe (HTML &#700;). Typists who are unfamiliar with Unicode frequently use an apostrophe instead, although this can cause problems in computers because apostrophe is a punctuation mark, not a word-building character, and the ambiguous use of apostrophe for two different functions can make automated processing of the text difficult. The Unicode character for saltillo is not included in the Unicode packages found in mobile phones also causing typists to have to revert to the apostrophe in order to avoid display issues for mobile users.